[lldb-dev] Is anyone using the gtest Xcode project?

Jonathan Roelofs jonathan at codesourcery.com
Thu Mar 12 18:05:09 PDT 2015

On 3/12/15 6:06 PM, Zachary Turner wrote:
> Wasn't really trying to get into an extended discussion about this, but
> FWIW I definitely realize that lldb's tests are more complicated than
> what lit currently supports.  But that's why I said "even if it meant
> extending lit".  It was mostly just a general comment about how it's
> nice if everyone is focused on making one thing better instead of
> everyone having different things.
> As for specifics, my understanding is that lit parallelizes better (so
> running tests is faster), understands how to build programs (so doesn't
> require makefiles), and has a richer language for specifying how and
> under what circumstances different tests should be run.  It's also
> familiar to other LLVM developers (so encourages cross-collaboration),
> and allows one to write self-contained tests with the program to test
> and the check in a single file (less maintenance).

I don't know much about lldb's testing needs, but I thought I'd chime in 
and mention that there's a lot of magic in the lit TestFormat (which 
testsuites can define themselves), and that it's waaaaay more flexible 
than it looks.

LLVM uses the ShTest test format a lot, and that one is well-suited for 
the process Jim describes: building shell script pipelines with checkers 
at the end, where the test file itself serves as both the input to the 
beginning of the pipeline, and the input to the checker at the end.

Libcxx and Libcxxabi have their own LibcxxTestFormat that behaves a 
little differently: they make the assumption that every test is a c/c++ 
file which needs to be compiled, executed, and that an exit status of 0 
is a pass.

 From a quick look at the lldb testsuite, I imagine if you wanted to 
LIT-ify it, it would make sense to have yet another TestFormat. This 
test format would know that it needs to look for *.py files, invoke the 
Makefile next to them (or put metadata in comments at the top of the 
*.py that says how to build it), then run the *.py file. I think the 
changes to the tests themselves would be minimal, as would writing the 
lit.cfg to glue it all together.


> In any case, I'm really not an expert on lit, so +bogner and +chandlerc
> in case they want to chime in.  I do think it's at least worth thinking
> about whether lit *could* be extended to meet LLDB's needs -- if nothing
> else as a thought exercise, and maybe learning more about how it works
> would give us some ideas to make our own test suite better.
> On Thu, Mar 12, 2015 at 4:39 PM <jingham at apple.com
> <mailto:jingham at apple.com>> wrote:
>      > On Mar 12, 2015, at 4:08 PM, Zachary Turner <zturner at google.com
>     <mailto:zturner at google.com>> wrote:
>      >
>      > Oh I'm all for reusing as much of the existing mechanism as
>     possible.  Was just stating how the CMake worked as a discussion
>     point.  Another possibility would be to just have the Xcode project
>     build one executable that pulls in sources recursively from the
>     entire subtree.  Is this as easy in Xcode as just adding all sources
>     from a subfolder to a single target?
>      >
>      > One day far off in the future it would be nice if all of LLDB's
>     tests were ported to lit (even if that meant extending lit to make
>     it do what we needed it to do),
>     Why would this be nice?  It looks like lit is a good test runner for
>     tests that have some input, do something with the input, produce an
>     output and check that output is matches some pattern.  That is not
>     at all what the lldb tests look like.  They often have to do complex
>     dances - for instance depending on how the line tables come out
>     there are many "correct" ways to step through code.  If you are
>     going to test this you've got to do "step, if I got to a close
>     bracket, step again, if I got past it don't.  Etc...
>     I see no benefit in extending a simple runner like lit to do the
>     complex dances the lldb testsuite sometimes has to do.  I'm all for
>     sharing, but it is also okay to have two implementations of some
>     functionality if the two uses are sufficiently different, and this
>     certainly seems like one of those cases.
>      > so I can definitely see some value in hooking lit up to the Xcode
>     build so it does everything the CMake build does.  I'll have to look
>     into exactly what steps the CMake and/or autoconf build are taking,
>     but I suspect it's going to involve running CMake from a script, so
>     not very desirable.  I'm still learning a lot of this stuff though,
>     so there may be a better way.  Either way, I'll have to look into it
>     a little bit.
>     Jim
>      >
>      > In the meantime, if running unit tests from Xcode is not part of
>     anyone's usual workflow, can I remove it for now?
>      >
>      > On Thu, Mar 12, 2015 at 4:01 PM <jingham at apple.com
>     <mailto:jingham at apple.com>> wrote:
>      > I'm not sure if this is what you meant, but I don't see a lot of
>     value in making an Xcode project that has targets for each of the
>     gtest binaries, and then tries to run the tests.  Seems to me it
>     would be better if the gtest project just invokes whatever mechanism
>     the cmake build would do to run the tests.  That's just another set
>     of things to keep in sync.
>      >
>      > It is sufficient to have a target that just does whatever steps
>     cmake/lit do to build the gtests & run them, if that is possible.  I
>     guess if you can't do this without running cmake in the lldb
>     top-level directory that would be a problem.  But it still seems
>     better to me to wire that up, than to have to add tests to both
>     Xcode & cmake.
>      >
>      > Jim
>      >
>      >
>      >
>      >
>      >
>      > > On Mar 12, 2015, at 3:46 PM, Zachary Turner <zturner at google.com
>     <mailto:zturner at google.com>> wrote:
>      > >
>      > > So I'm guessing the scheme runs do-gtest.py.  I'd like to
>     delete that file as well as all the Makefiles in the directory if
>     possible.  It seems like these files should be built using the
>     normal Xcode build system the same way the rest of LLDB is built.
>      > >
>      > > The way the CMake does it is that each test folder generates a
>     new executable.  So right now it will build HostTests.exe,
>     ProcessLinuxTests.exe, and UtilityTests.exe.  And then CMake will
>     invoke lit (the LLVM test runner) to run each of the executables one
>     by one and print the output.
>      > >
>      > > I'm not sure if that's easy or feasible to do in the Xcode
>     build.  I kind of don't want to leave this do-gtest.py and Makefiles
>     in the build though, because the more of this stuff we have the more
>     maintenance it is, and things tend to rot.
>      > >
>      > >
>      > > On Thu, Mar 12, 2015 at 3:23 PM <jingham at apple.com
>     <mailto:jingham at apple.com>> wrote:
>      > > Xcode has "projects" and then "workspaces" and "schemes".
>     Workspaces aggregate projects.  Schemes exist in both workspaces and
>     projects and are the way to say "do something with some of the stuff
>     referred to by this project/workspace."  So the way to do this
>     formally is to have the gtest scheme build & run the tests from the
>     gtest project.
>      > >
>      > > The lldb.xcworkspace file does reference the gtest xcode
>     project, and it has a scheme for the gtest.
>      > >
>      > > Not sure what the scheme does yet, I'll look in a few minutes
>     if nobody beats me to it, I'm in the middle of things right now.
>      > >
>      > > Jim
>      > >
>      > >
>      > >
>      > > > On Mar 12, 2015, at 2:41 PM, Zachary Turner
>     <zturner at google.com <mailto:zturner at google.com>> wrote:
>      > > >
>      > > > In lldb/gtest there is a gtest.xcodeproj folder with what I
>     guess is an Xcode project.  If I understand the way Xcode works, the
>     way to use this is by opening this in another instance of Xcode
>     separate from your normal LLDB project, and then building it.  Is
>     this right?
>      > > >
>      > > > I have a patch that moves some files around, and if nobody is
>     using this Xcode project, I would like to delete it.  Then, after I
>     get the tests up and running in the CMake build, we can add it to
>     the "real" Xcode project as a separate target similar to how you
>     currently run the LLDB Test suite.
>      > > >
>      > > > Any objections to deleting the Xcode project?
>      > >
>      >
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Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded

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